[AZ] {2,4}, not limiting between 2 and 4 characters

Question

PCRE: /\A[A-Z0-9_\.%\+\-]+@(?:[A-Z0-9\-]+\.)+(?:[a-z]{2,4}|museum|travel)\z/i 
POSIX: /^[A-Z0-9_\.%\+\-]+@(?:[A-Z0-9\-]+\.)+(?:[A-Z]{2,4}|museum|travel)$/i

This regular expression is correct in every way for my needs, except that it allows you to send emails such as [e-mail]. He says this is a match. If I’m not mistaken, does {2,4} after [AZ] not mean that it should be from 2 to 4 characters? Maybe this is a problem with a quarrel, a museum and travel? I have confirmed that this is allowed in my application, and several regular expression testers. Also, I'm fuzzy about what PCRE and POSIX really did. I am afraid that they might just be PCRE, and I laugh. AFAIK, JavaScript is POSIX, and Ruby is PCRE. So if I didn’t get it right, please forgive me , it was a long, long night of learning regular expressions, in and out, and I'm trying to look badass. :)

Answer 1

It does, but applies only to the top-level domain name ("com" in your example).

Answer 2

Ruby regex documentation:

• Ruby 1.8: http://ruby-doc.org/docs/ruby-doc-bundle/Manual/man-1.4/syntax.html#regexp
• Ruby 1.9: http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt

Answer 3

POSIX , (?:group), POSIX. JavaScript POSIX. JavaScript - Perl-, . . regex .